Progress Report

Rio Grande Silvery Minnow Population Monitoring During April 2024

URL: https://webapps.usgs.gov/mrgescp/documents/202404-RGSM-Population-Monitoring-Monthly-Report.pdf

Date: 2024/05/15

Author(s): Dudley R.K., Platania S.P., White G.C.

Publication: Contract 140R4019P0048/Requisition 0040613161. Submitted to: U.S. Bureau of Reclamation, Albuquerque Area Office, 555 Broadway NE, Suite 100, Albuquerque, NM 87102.

Abstract:

The April 2024 population monitoring efforts were conducted at the 20 standard sites and 20 additional sites. We sampled the ten old additional sites, along with ten new additional sites, during April 2024. Ten sites were in the Angostura Reach, fourteen sites were in the Isleta Reach, and sixteen sites were in the San Acacia Reach. For the 2024 monthly trends, data were based on all sites (i.e., standard, additional, and replacement sites) to maintain consistency across all monthly reports. A list of all collection localities is appended (Appendix A). Adult and juvenile fish were obtained by rapidly drawing a 3.0 m x 1.8 m small-mesh (ca. 5 mm) seine through discrete mesohabitats. Larval fish were collected with a 1.2 m x 1.2 m fine-mesh (ca. 1 mm) seine. All fishes were identified to species and enumerated. We used length-age relationships to assign ages (i.e., age-0, age-1, and age-2+) to all Rio Grande Silvery Minnow collected. Age-0 individuals are only present, however, after seasonal spawning events that typically first occur during spring runoff. Figures illustrating fish densities (i.e., fish per 100 m2) were prepared for the ten focal species to facilitate comparisons across reaches.